In the Switches column in the timeline, the second switch from the left, you'll find the continuously rasterize icon. It looks like a little sun. Turn it on, and providing that the composition window is set to Full resolution and Pixel Aspect Ratio Correction is turned off for non square PAR comps, your vector layers will look sharp in the Comp window and render just fine.
Some effects applied to Illustrator objects force rasterization of these layers in After Effects. In this case you can change the document raster settings in Illustrator and re-save the file to make them behave better, or you can remove the layer effects that are causing the problems and duplicate the effect in AE. There are no layer effects that force rasterization that cannot be duplicated inside AE.
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I can't find it anymore in CS4...
It's still there. Just toggle the modes/ switches (F4) and it should appear. For the record: it's called "continuously rasterize/ collapse transformations switch".
Not sure how I could have missed that one...
Thank you both!
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